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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 36 |
| 5 | 210 |
| 6 | 3150 |
| 7 | 55104 |
| 8 | 890232 |
| 9 | 16735944 |
| 10 | 386223120 |
| 11 | 9790441056 |
| 12 | 265867900056 |
| 13 | 7943197796352 |
| 14 | 260063260578576 |
| 15 | 9156071916788544 |
| 16 | 344740627648393920 |
| 17 | 13880862578534022720 |
| 18 | 595178180505073088640 |
| 19 | 27035591386823290224000 |
[1,0,0,6,36,210,3150,55104,890232,16735944, 386223120,9790441056,265867900056,7943197796352, 260063260578576,9156071916788544, 344740627648393920,13880862578534022720, 595178180505073088640,27035591386823290224000] |